Subtilisin-type proteases are well known in liquid aqueous detergents, particularly for use on laundry washing. A generally encountered problem in such liquid detergents is the degradation by the subtilisin of other enzymes in the composition and of the subtilisin itself. Consequently, the stability of the subtilisin and other enzymes in the liquid detergent composition is reduced, resulting in a liquid detergent with a reduced wash performance.
The prior art has dealt extensively with improving the storage stability of enzymes in liquid detergents, for example by adding various subtilisin inhibitors or stabilizers. Boric acid and boronic acids are known to reversibly inhibit proteolytic enzymes.
The use of peptide aldehydes for stabilizing certain proteases in liquid detergents is disclosed in WO 94/04651, WO 98/13458, WO 98/13459, WO 98/13460 and WO 98/13462. More specifically, WO94/04651 discloses the use of the peptide aldehydes Phe-Gly-Ala-PheH and Phe-Gly-Ala-LeuH for stabilizing subtilisin-type proteases. WO94/04651 also discloses Leu-Leu-TyrH as a suitable peptide aldehyde for stabilizing chymotrypsin-type proteases. Furthermore, WO94/04651 proposes methyl carbamate or methyl urea as an N-terminal protecting group of the peptide aldehydes. WO98/13460 discloses the use of peptide protease inhibitors, either peptide aldehydes or trifluromethyl ketones, where the peptide chain contains 2-5 amino acids and the aldehyde/trifluromethyl ketone is derived from the amino acids alanine, valine, isoleucine, leucine, phenylglycine, phenylalanine or homophenylalanine and where the N-terminal protection group is preferably a sulphonamide or amidophoshate.
WO2007/141736, WO2007/145963 and WO2007/145964 disclose the use of a reversible peptide protease inhibitor to stabilize liquid detergent compositions. US2003/157088 describes compositions containing enzymes stabilized with inhibitors.
WO 96/41638 and WO 2005/105826 disclose peptide aldehydes and ketones.